1. Technical Field
The present invention relates to a liquid crystal display device and an electronic apparatus.
2. Related Art
Flat panel display devices are now used widely in various types of monitors such as for computers as well as in display elements such as for cellular phones. It is predicted that the use of the flat panel display devices will continue to spread more widely, as they are being developed for use in wide-screen TVs. Of all the flat panel displays, the most widely used is a liquid crystal display, which often employs a color display system called a micro color filter system.
The micro color filter system is a system that can easily exhibit high reproduction performance, in that full color display is performed by dividing one pixel into at least three sub-pixels and by forming, in each sub-pixel, color filters of three primary colors of red (R), green (G), and blue (B). However, by the micro color filter system, it is difficult to satisfactorily increase light utilization efficiency because of color absorption and the like by the color filters. In a transmission-type liquid crystal display device having a backlight or in a reflection-type liquid crystal display device having a front light, such poor light utilization efficiency becomes the cause for increase in electricity consumption by the backlight or the front light.
In contrast, an electrically controlled birefringence (ECB) type liquid crystal display device is known as the color liquid crystal display device that does not use color filters (e.g., see “Liquid Crystal Device Handbook,” edited by the 142nd Committee of Japanese Institute for the Promotion of Technology (Nippon Gakujutsu Shinkokai), published by Nikkan Kogyo Shinbunsha, 1995, pp. 346-348). When a voltage is applied to a liquid crystal cell, birefringence in the cell changes as a result of a change in the liquid crystal molecule alignment due to dielectric anisotropy of the liquid crystal. When the liquid cell is placed between two polarizing plates, the change in the birefringence emerges as a change in light transmission. This is called an electrically controlled birefringence (ECB) effect. With the ECB-type liquid crystal display device, display is performed by taking advantage of such an effect.
In the present specification, refractive index may mean a general refractive index or the above-referenced birefringence and is not limited to one or the other.
The following explains the operational principles of the ECB-type liquid crystal display device.
A homogenous cell using liquid crystal having a refractive index anisotropy Δn and a cell thickness d is placed between two polarizing plates (a polarizer and an analyzer). When angles of a director axis of liquid crystal molecules to the polarizer and to the analyzer are Ψ and χ, respectively, a retardation R and a phase difference δ between extraordinary light and ordinary light that are generated when light passes through the cell are expressed below by the equations (1) and (2), respectively.R=Δn×d  (1)δ=2πR/λ=2π×Δn×d/λ  (2)
Further, a transmission intensity of light (J) entering perpendicularly to the cell is expressed in the equation (3).J=A2{ cos2(Ψ−χ)−sin 2 Ψ sin 2 χ sin2(δ/2)}  (3)
Further, when the two polarizing plates are crossed perpendicularly to each other, and (χ−Ψ=π/2) and Ψ=π/4, the transmitted light intensity J is expressed in the equation (4).J=A2 sin2(δ/2)=A2 sin2(πΔnd/λ)  (4)
These equations indicate that the transmitted light intensity depends on the retardation R when monochrome light is used, and various color phases are exhibited depending on the retardation R when white light is used as the light source. When voltage is applied to the liquid crystal cell, the retardation R changes since the effective refractive index anisotropy in the cell changes along with the liquid crystal molecule alignment. Based on the explained principles, the ECB-type liquid crystal display device controls the transmitted light intensities and display colors by the application of voltage in order to carry out the display.
With a generally-used color liquid crystal display device that employs a system such as a liquid crystal light valve system in combination with color filters, only one color is displayed with one sheet of cell or with one pixel, while the ECB-type color liquid crystal display device enables the color display relatively stably due to its simple structure using one sheet of cell and two polarizing plates.
However, with the conventional ECB-type color liquid crystal display device, the volume of the applied voltage must be controlled precisely in order to change the color phases to be displayed.
Further, with the conventional ECB-type color liquid crystal display device, even if the pixel is divided into display regions of each color, the lights interfere with each other among the regions and, thus, vivid color display has been difficult. Also, because the retardation R changes greatly depending on the visual angle, the strong visual angle dependency of the display color has been a problem.